You can rip YouTube videos from the command line in Linux and OSX. There could be ways to do this in Windows via Cygwin, but I did not try that.
In Debian Linux, or any other distribution that uses the apt or aptitude package manager, you can get the youtube-dl program by pulling them from the repositories. Run the following command on a terminal window
sudo apt-get update && sudo apt-get install youtube-dl youtube-dl <youtube vid URL>
It’s also available on macOS. If you use brew, you can get it with this
brew update brew install youtube-dl youtube-dl <youtube vid URL>
I think you can also do this in Windows with Cygwin, but I haven’t tried that.